In one aspect, the present invention relates to olefin polymer films and, in particular, to olefin polymer films having a combination of physical properties making them especially well suited for use as stretch/cling films in various packaging and/or palletizing applications. In another aspect, the present invention relates to biaxially oriented films of ethylene/higher .alpha.-olefin copolymers having a tackifying agent incorporated therein.
In the packaging and/or palletizing art, it is known to package individual articles and/or to bundle together or palletize a plurality of articles using a so-called "stretch wrapping" technique. According to such technique, a relatively thin film web of a polymeric material is stretched or elongated, thereby creating tension in said film web, while being wrapped several times around the article or articles to be packaged or palletized. Upon the release of the stretching or elongating forces at the conclusion of the wrapping operation, the film attempts to relax or spring at least partially back to its original non-stretched dimension thereby tightly or snuggly engaging the article or articles wrapped therein. In connection with such a stretch wrapping operation, it is possible in theory to secure the stretched and wrapped film in place around the packaged article or articles in a variety of ways (i.e., so as to prevent the stressed or tensioned film from returning or relaxing back to its original dimensions without imparting the desired packaging integrity to the packaged article or articles encompassed thereby). However, as a matter of practical expediency, efficiency and economy, it is common practice to employ film which exhibits sufficient cling to itself to hold said film in place around the packaged article, to prevent significant slippage of the stretched overlaid film layers, and to thereby prevent relaxation or shrinkage of said film back to its original pre-packaging unstretched dimensions.
While a variety of films are currently available on the commercial market for use in stretch/cling packaging or palletizing operations, such currently available films all suffer from one or more notable deficiencies, drawbacks, or limitations. For example, some of the films which are currently available are produced via cast film processes. While such cast films are typically characterized by having high Elmendorf tear ratings in the transverse direction, they also generally have relatively low tear resistance in the machine direction. As such, these cast films have a pronounced tendency to tear on the corners or at other sharp protrusions of articles being stretch wrapped or palletized therewith. On the other hand, certain other currently available stretch/cling films, such as those produced by conventional blown film processing techniques, generally have a more acceptable balance between their Elmendorf tear ratings in the machine and transverse directions, but are generally less than totally satisfactory in terms of certain other properties such as, for example, their cling properties, particularly at high degrees of elongation.
In view of the foregoing deficiencies of the stretch/cling films available to date, it would be highly desirable to provide a polymeric film having the proper combination of properties to overcome said deficiencies and to thereby be especially well suited for use as a stretch/cling film for packaging and palletizing end-use applications.